linux-kernel - Re: [PATCH 1/2] pstore: Make default pstorefs root dir perms 0750

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Date:   Wed, 16 Aug 2017 17:05:02 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, Nick Kralevich <nnk@...gle.com>,
        Sebastian Schmidt <yath@...h.de>,
        Tony Luck <tony.luck@...el.com>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Patrick Tjin <pattjin@...gle.com>,
        Mark Salyzyn <salyzyn@...gle.com>
Subject: Re: [PATCH 1/2] pstore: Make default pstorefs root dir perms 0750

Hello,

On (08/10/17 13:36), Kees Cook wrote:
> Currently only DMESG and CONSOLE record types are protected, and it isn't
> obvious that they are using a capability check. Instead switch to explicit
> root directory mode of 0750 to keep files private by default.  This will
> allow the removal of the capability check, which was non-obvious and
> forces a process to have possibly too much privilege

it's CAP_SYSLOG, isn't it? is it too much? does chgrp require less privileges?

	-ss

> when simple post-boot chgrp for readers would be possible without it.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  fs/pstore/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
> index fefd22611cf6..f1e88b695090 100644
> --- a/fs/pstore/inode.c
> +++ b/fs/pstore/inode.c
> @@ -471,7 +471,7 @@ static int pstore_fill_super(struct super_block *sb, void *data, int silent)
>  
>  	inode = pstore_get_inode(sb);
>  	if (inode) {
> -		inode->i_mode = S_IFDIR | 0755;
> +		inode->i_mode = S_IFDIR | 0750;
>  		inode->i_op = &pstore_dir_inode_operations;
>  		inode->i_fop = &simple_dir_operations;
>  		inc_nlink(inode);
> -- 
> 2.7.4
>